It does not matter that he is not anemic right now. Macrocytosis will precede development of an anemia, and can by itself be a clue to disease process.
To the OP:
This is a common lab abnormality seen in an otherwise seemingly healthy outpatient - 'macrocytosis' - elevated MCV without anemia.
Your results could be within the range of normal, as your doctor is telling you. There is small percentage of people whose MCV is greater than 100 but are 'normal variants', although they are usually on the older side. How old are you? However, I would not ordinarily assume this until other causes of macrocytosis have been ruled out.
The recommended follow-up testing for macrocytosis is as follows:
TSH (test for hypothyroidism or low thyroid)
Retic count
vitamin B12/Folate levels (testing for vitamin deficiencies)
peripheral smear of blood
possibly serum protein electrophoresis
As the poster above mentioned, liver disease/alcoholism would be a consideration but your liver labs are normal and you are not an alcoholic.
You are not iron deficient - if you were, your MCV would be low.
Prior complete blood counts would be helpful in figuring out whether the macrocytosis is new or not.
If all these tests were to come back negative, your bloodwork is probably normal and you may be overtraining.
Hope this helps.